DevTools: extract the dom_extension module.

third_party/WebKit/Source/devtools/front_end/dom_extension/DOMExtension.js

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 794 matching lines @@
   return event.keyCode !== 229 && event.key === 'Enter';
 }
 
 /**
  * @param {!Event} event
  * @return {boolean}
  */
 function isEscKey(event) {
   return event.keyCode === 27;
 }